Hua Hin, Thailand — A series of blasts hit three of the most popular tourist resorts in southern Thailand on Thursday and Friday, killing two people and wounding dozens, just days after the country voted to accept a military-backed constitution in a referendum.

Twin blasts hit the upscale resort of Hua Hin, around 200 kilometers (125 miles) south of Bangkok, on Friday morning just hours after two bombs killed one person and wounded 21 late on Thursday.

Hua Hin is home to the Klai Kangwon royal palace, which translates as "Far from Worries Palace," where King Bhumibol Adulayadej, the world's longest reigning monarch, and his wife Sirikit have often stayed in recent years.

One person died and three people were wounded in one of the Friday morning blasts near an iconic clock tower in Hua Hin, deputy police spokesman Police Colonel Krisana Pattanacharoen told reporters in Bangkok.

Two small bombs exploded in the tourist beach town of Patong on Phuket island and two more in Phang Nga, another tourist region north of Phuket on Friday, local police said. One Thai man was lightly wounded in Patong, police said.

Police believe the series of blasts were acts of local sabotage and not linked to any international militant group, deputy police spokesman Police Colonel Krisana Pattanacharoen told reporters on Friday.

"It's too soon to jump to any conclusion," he said "But what we know for sure is that the incidents are not linked directly to any kinds of terrorism, in fact it's local sabotage and we are trying to identfy those responsible behind the scenes.

"There are no conflicts in the country that may lead to terrorists being in the country. That's why we can say that these incidents are not terrorist attacks," he said.�

Police also said they have not found any evidence that the blasts were coordinated or whether they were related to an insurgency in Muslim-majority provinces in southern Thailand.

TRAVEL ADVISORY

Australia issued a travel advisory saying Australians should "exercise a high degree of caution" and warned: "Further explosions in any part of Thailand are possible."

The Friday morning blasts in Hua Hin came after a bomb exploded near a bar in the town late on Thursday that killed one Thai woman and wounded 21 people, Police Col. Krisana said.

Nine of those injured in Thursday night's twin blasts in Hua Hin were foreigners, Hua Hin deputy police chief Samer Yousamran said. Those twin explosions were detonated by mobile device, police said. The first took place 20 minutes earlier and about 50 meters from the second, but injured nobody.

Twin blasts are common in the three Muslim-majority southernmost provinces of Thailand, where a bloody insurgency has killed more than 6,500 people since 2004.

The three provinces soundly rejected the referendum on the new military backed constitution which passed overwhelmingly in the rest of the country in Sunday's vote.

Violence has occasionally spilled over to areas outside the three provinces, which were part of a Malay sultanate until it was annexed by Buddhist-majority Thailand a century ago.

Hua Hin, Phuket and Phang Nga are far from the usual conflict zone, where attacks typically target security forces and not tourists.

In a separate incident on Friday, Thai media reported two bombs had exploded in the southern province of Surat Thani, killing one person and wounding five.

The head of Interpol in Thailand, Police Major General Apichat Suriboonya, told Reuters he needed more information befor deciding "whether it is terrorism or not."

"But the thing is, if you observe the bombs, they are not targeted to kill people but to send a message to some groups. It could be a domestic issue."

POLITICAL TURMOIL

Small improvised bombs have been used frequently for attacks during periods of unrest over the past decade of political turmoil in Thailand.

However, such attacks have been rare since the military seized power in a May 2014 coup.

The latest bombings came almost a year after an attack on a Hindu shrine thronged with tourists in central Bangkok killed 20 people and wounded more than 120. Thai police have accused two ethnic Uighur Muslims for the Aug. 17, 2015, attack.

King Bhumibol and his wife Sirikit are both in hospital in Bangkok and have not resided recently at their palace in Hua Hin. Check points have been established and security beefed up around Hua Hin and a royal palace in the resort.

King Bhumibol has received treatment for an infection over the past month in a Bangkok hospital, the Royal Household Bureau said on Aug. 1. Concern about the health of the king and nervousness over the succession have played into the country's political tensions.